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Feline upper respiratory syndrome (Proceedings)

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Nov 01, 2009

Feline upper respiratory infection (URI) is perhaps the most frustrating illness facing shelter veterinarians, managers and staff. Many cats are chronically infected, vaccines are partially effective at best, and specific treatments are limited. URI is very easily spread by fomites or droplet transmission, and some URI agents are resistant to disinfection. Factors such as overcrowding, poor air quality, poor sanitation, stress, concurrent illness, parasitism, poor nutrition, and other causes of immunosuppression predispose to disease, and many of these factors are difficult or impossible to completely eliminate in a typical shelter, cattery or rescue home.

In spite of these challenges, some shelters and catteries clearly suffer less from URI than others. Although URI can never be totally eradicated, the frequency and severity of cases can be greatly reduced through a systematic management strategy. Focusing on treatment rather than prevention will result in frustration. Instead it is more prudent to concentrate on reduction of overcrowding, effective cleaning and stress control.

Specific agents most commonly associated with URI

Any of the agents listed below can be a primary cause of URI. Approximately 80-90% of cases are most likely caused by one of the two viruses listed. However, environmental factors and animal immune status play an equally important role in causing actual disease; all the pathogens listed below can also be found in clinically healthy cats.
1. Feline Herpesvirus-1 (FHV-1 - probably the most common)
2. Feline Calicivirus (FCV - perhaps not as common as herpes, but potentially more severe)
3. Chlamydophila felis
4. Mycoplasma spp.
5. Bordetella bronchiseptica

Diagnosis

Most often, a causative agent is not identified in individual cases of URI. Sometimes a best guess can be made based on clinical signs: FCV is more likely to be associated with oral ulceration or limping, FHV-1 is more likely to cause keratitis or corneal ulceration. However, all can cause overlapping signs of URI as well as be isolated from clinically normal cats. Preventative measures (and treatment) tend to be the same for all causative agents. However there are circumstances under which laboratory diagnostics have value. Diagnostic options include viral and bacterial culture and PCR on conjunctival or oropharyngeal swabs (and occasionally other samples, such as tracheal washes or lung tissue). Samples should be obtained from the most prominently affected location. Some circumstances under which diagnostic testing should be considered:
     • Unusual signs, severity or frequency of disease in a population of cats
     • Legal issues (e.g. hoarding investigation, liability concerns)
     • Detect carriers (e.g. low turnover shelter that has recurrent severe disease)
     • Individual cat that has not responded to empirical therapy, especially before initiating expensive or risky treatment.
Idexx laboratories now offers a diagnostic PCR panel to look for the five common pathogens listed above (http://www.idexx.com/animalhealth/laboratory/realpcr/tests/furd.jsp)

Prevention of feline URI

Population management

Crowding and the attendant stress is undoubtedly the single greatest risk factor for severe respiratory (and other) disease outbreaks in populations. Increased population density leads to a greater risk of disease introduction, higher contact rate, reduced air quality, and often, compromises in housing and husbandry. Unfortunately, crowding in shelters is not uncommon, either due to insufficient facilities to provide even minimal care for the stray population, or (as is increasingly common) a well-intended attempt to decrease euthanasia by housing more animals. Tragically, such efforts may not only fail to improve the number of animals adopted, they may actually lead to increased disease and death1. Even in a boarding facility or vet clinic, it is important to anticipate times of peak population, recognize that these will be periods of increased risk for respiratory disease outbreaks, and plan sufficient additional staff so that husbandry is not compromised.

An under appreciated strategy for respiratory disease prevention is to simply reduce the amount of time each cat spends in the shelter environment. Length of stay has been shown in several studies to be a significant risk factor for development of feline URI2,3. Reducing length of stay may not be possible (or desirable) in a boarding facility or vet hospital, but management practices that increase length of stay for shelter cats should be carefully assessed to ensure the benefit of these practices outweighs the risk of disease they may create. This could include routine quarantine of apparently healthy animals, delays created by backlogs in behavior assessment or surgery, or failure to move cats to public-viewing areas of the shelter as soon as they are available for adoption. Increased time for each cat in the shelter also contributes substantially to increased crowding with all the associated risks.